assign_attributes not working

I just signed up for Payments with Stripe and Rails Master Class and am loving it...can't walk away from it; learning a ton!

Having an issue though and was hoping someone could lend a hand. I am following the videos exactly and the only thing I can see that is different is the videos are using the Stripejs form example from Stripe.com whereas I am using Elements. There is an Elements section in the videos which is why I implemented it, but the videos continue without it. Either way, things seem to be working ok, well - until this snag. Oh, even with the attributes not being assigned, Stripe is still creating/updating users properly.

I am trying to assign_attributesif params[:card_last4] but the attributes are not saving so I am not able to display card_brand, card_last4 etc.. Below is my code, thank you.

Sometimes I have done virtual attributes on the User (like "user[card_"+field+"]")) and other times just directly accessing the param. It doesn't really make a difference which way you go, but the virtual attributes can make it nice to assign all the fields and then do the saving in a method on the model rather than in the controller.